Almost every surgical treatment carries a risk that bodily tissues exposed during the course of the surgery will adhere to each other, a condition termed an adhesion. Gynecological and abdominal surgeries, in particular, are prone to causing adhesions, which often have the appearance of scar-like masses. Adhesions are frequently painful and are a significant cause of infertility resulting from gynecological surgeries. Adhesions caused by surgeries are often called surgical adhesions.
One approach to the treatment of adhesions has been to coat surgically exposed tissues with a gel before closing the surgical site. Gels of various types have been used, including suspensions of colloidal particles, and pastes of natural polymers. Various examples of some of these approaches are described in U.S. Pat. Nos. 6,020,326 and 5,605,938. Some of these approaches allow for the polymers to be added to the patient “in situ” in a solution and then chemically reacted inside the patient so that the polymers form covalent crosslinks to create a polymer network. This approach lets the polymer be formed in a way that closely conforms to the shape of the tissues in the body, as described, for example, in U.S. Pat. Nos. 5,410,016; 5,573,934 and 5,626,863.
Hydrogels are especially useful for use in the body because they are more biocompatible than non-hydrogels and are thus better tolerated in the body. Besides being useful for post-operative adhesions they can be used for many medical purposes, such as tissue augmentation, medical device coating, surgical sealing, and drug delivery. Examples of hydrogels formulated for such purposes are found in U.S. Pat. Nos. 4,414,976; 4,427,651; 4,925,677; 5,527,856; 5,550,188; and 5,814,621.
Crosslinked polymers have previously been formed using polymers equipped with either electrophilic or nucleophilic functional groups. For example, U.S. Pat. Nos. 5,296,518 and 5,104,909 to Grasel et al. describe the formation of crosslinked polymers from ethylene oxide rich prepolymers, wherein a polyisocyanate or low molecular weight diisocyanate is used as the electrophilic polymer or crosslinker, and a polyoxyethylene based polyol with in situ generated amine groups is used as the nucleophilic precursor; see also U.S. Pat. Nos. 5,514,379; 5,527,856; and 5,550,188.
Polymeric hydrogels, for example, fibrin glue, crosslinked proteins, and crosslinked polyethylene oxides, are essentially colorless. This problem is often even more acute when the hydrogel is applied as a coating on a tissue because tissue coatings conventionally are thin. The resulting colorless solution or film is therefore difficult to visualize, especially in the typically wet and moist surgical environment. Under laparoscopic conditions, visibility is even more difficult due to the fact that only a two-dimensional view of the surgical field is available on the monitor that is used in such procedures.